Authors: Hu, R; Walsh, SDC; Missen, J; Anderson, N

Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2025_87

Cite As:
Hu, R, Walsh, SDC, Missen, J & Anderson, N 2020, 'Simulating fracture network permeability in brown-coal slopes', in PM Dight (ed.), Proceedings of the 2020 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering, Australian Centre for Geomechanics, Perth, pp. 1281-1290, https://doi.org/10.36487/ACG_repo/2025_87

Download citation as:   ris   bibtex   endnote   text   Zotero


Abstract:
Slope stability of open cut brown-coal mines depends upon the permeability of the fracture network within the coal seam. In this paper, we provide a detailed analysis of the role of the fracture distribution on the permeability of brown-coal slopes and outline a model to capture this behaviour. Brown coal is relatively impermeable, but heavily fractured. Hence, a stress-dependent fracture permeability model is employed that considers the spacing, orientation, aperture and frequency of the fractures to produce an effective permeability. We discuss how this model captures fracture heterogeneity and the effect of changing stress conditions on the fluid flow. Fracture data collected from real mines exhibit significant degrees of heterogeneity, in particular, they may include a wide range of apertures and inter-fracture separations. The results of the effective permeability model demonstrate that in many cases slope permeability is dominated by highly permeable but low probability fractures. These results emphasise the need for models capable of capturing the effects of heterogeneity and uncertainty on the slope behaviour.

Keywords: lignite, fractured media, effective continuum models, numerical simulation

References:
Adhikary, DP & Wilkins, A 2012, Reducing the Impact of Longwall Extraction on Groundwater Systems, CSIRO, Collingwood.
AGL 2017, Ground Control Management Plan, Revision 03, internal report.
AGL 2018, ‘AGL Loy Yang Mine Sustainability Report 2017–2018’, AGL,
AGL 2019, AGL Loy Yang Power Station, viewed 9 October 2019,
Barton, N, Bandis, S & Bakhtar, K 1985, ‘Strength, deformation and conductivity coupling of rock joints’, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, vol. 22, no. 3, pp. 121–140.
Chen, M, Bai, M & Roegiers, JC 1999, ‘Permeability tensors of anisotropic fracture networks’, Mathematical Geology, vol. 31, no. 4, pp. 335–373.
Chen, D, Pan, Z & Ye, Z 2015, ‘Dependence of gas shale fracture permeability on effective stress and reservoir pressure: Model match and insights’, Fuel, vol. 139, pp. 383–392.
Meng, ZP, Zhang, JC & Wang, R 2011, ‘In situ stress, pore pressure and stress-dependent permeability in the Southern Qinshui Basin’, International Journal of Rock Mechanics & Mining Sciences, vol. 48, pp. 122–131.
Pan, Z & Connell, LD 2012, ‘Modelling permeability for coal reservoirs: A review of analytical models and testing data’, International Journal of Coal Geology, vol. 92, pp. 1–44.
Renshaw, CE 1995, ‘On the relationship between mechanical and hydraulic apertures in rough-walled fractures’, Journal of Geophysical Research, vol. 100, no. B12, pp. 24629–24636.
Seidle, JP, Jeansonne, DJ & Erickson, DJ 1992, ‘Application of matchstick geometry to stress dependent permeability in coals’, Proceedings of the Rocky Mountain Regional Meeting 1992, Society of Petroleum Engineers, Inc., Richardson, pp. 433–444.
Snow, DT 1969, ‘Anisotropic permeability of fractured media’, Water Resources Research, vol. 5, no. 6, pp. 1273‒1289.
Tan, Y, Pan, Z, Feng, X, Zhang, D, Connell, LD & Li, S 2019, ‘Laboratory characterisation of fracture compressibility for coal and shale gas reservoir rocks: A review’, International Journal of Coal Geology, vol. 204, pp. 1–17.
Zhang, L, Aziz, N, Ren, T, Nemcik, J & Wang, Z 2012, ‘Permeability testing of coal under different triaxial conditions’, Proceedings of the 12th Coal Operators' Conference, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 277–285.
Witherspoon, PA, Wang, JSY, Iwai, K & Gale, JE 1980, ‘Validity of Cubic Law for fluid flow in a deformable rock fracture’, Water Resources Research, vol. 16, no. 6, pp. 1016–1024.




© Copyright 2020, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
Please direct any queries or error reports to repository-acg@uwa.edu.au